Essential oils have been known for many years to have different desired properties, such as: antiseptic, disinfectant, antifungal, antibacterial etc. Consequently, essential oils have been used as natural products for a number of uses. Over the years, they have been replaced with less expensive but effective synthetic chemical agents, but—given the toxicity and environmental effects of these synthetic chemicals, there is a rising interest in using once more the natural essential oil agents. This objective necessitates the development of formulations that combine the desired properties of the natural essential oils while matching the efficacy of synthetic agents, at a low cost. This requires that the essential oils be formulated in cost effective controlled release rate carriers which release the essential oils at low but effective concentrations. It also requires that the entities carrying the essential oil be readily formulated into configurations for a given application.
WO 04/098767, by the inventors of the present application, discloses a process for the preparation of essential oil microcapsules by encapsulation of an essential oil through interfacial polymerization, whereby a polyurea and/or polyurethane film is formed around the liquid essential oil droplets. These microcapsules may be used as disinfectant products for the consumer market as hard-surface cleaners, laundry detergents and softeners, as pesticides, insect repellents, and as antiviral or antifungal agents.
WO 06/07756, also by the inventors of the present application, discloses agricultural formulations of essential oil microcapsules and uses thereof, which were also prepared by interfacial polymerization, and comprise a combination of a volatile essential oil and a non-volatile carrier. The microcapsules were a liquid core of essential oil optionally with additives and other active agents such as IGRs.
More recently, WO 07/094,000, also by the inventors of the present application, disclosed an aqueous (“green”) method for preparing microcapsules comprising essential oils, by mixing at least one alkanoic acid with at least one essential oil; adding an aqueous basic solution to obtain a suspension; and mixing into this suspension an aqueous salt solution comprising a multivalent cation, which complexed with the acids groups of the alkanoic acids.
There is an going need of developing new formulations that would be better suited to address essential microcapsule characteristics needed by different industries.
For example, crops such as bananas, mangoes, peppers and carrots often become biologically contaminated by bacteria and/or fungi post-harvest. Contamination can be initiated pre-harvest (eg. by parasitic presence at the time of picking/harvesting), during harvesting (eg. where contaminants are introduced by mechanical harvesters or human intervention) and post-harvest (eg. where parasites and spore settle on post-harvested produce). Regardless of the time of contamination, it is necessary to treat harvested fruit, vegetables and plants prior to transportation and storage to eradicate any such contamination, as in fact is required by international authorities. Furthermore, post harvest treatment increases the shelf life of the crops and enables longer transportation and storage thereof.
So far, a variety of synthetic pesticides have been used to treat post-harvest crops, mostly by dipping (see for example U.S. Pat. No. 6,030,927) but there is an ever-increasing international concern over the residues of such pesticides on the treated fruits and vegetables.
Not only crops, but other foods, leather products, fur coats and products of paints and pastes formed of starch or cellulose, are prone to mold (a fungus that produces a superficial growth on various kinds of damp or decaying organic matter) or develop an increased growth of harmful microorganisms, mostly of bacteria. This considerably reduces the shelf life of these products.
Known methods to prevent such contamination of products are by seal-packing the product with an oxygen absorber to maintain a low oxygen concentration within the package, by sealing the product in an ethanol environment, or by using synthetic anti-fungal and anti-bacterial agents. Each of these methods is limited and has known disadvantages.
Preferably, it would have been desirable to find a treatment method which would use natural active ingredients, and that the actual formulation would be placed in close proximity to the product to be protected but would avoid direct contact with the treated crop or product.
For certain other applications, it is important to be able to control flying insects for several hours, in both indoors or outdoor environments. Traditionally, articles or devices that dispense insecticide vapors to control such insects in such settings require heating or burning a liquid or solid substrate to evaporate the active ingredients (for example, citronella candles and similar products). Alternative methods include employing passive evaporation of insect control active ingredients without the application of heat, but their application is quite limited: for example, U.S. Pat. No. 4,130,450 discloses an insecticide-impregnated, open, low-density web that provides an expanded surface that may be loaded with contact insecticides, preferably micro-encapsulated pyrethrum, that is then evaporated to repel insects, such as flies or mosquitoes. Whitcomb mentions that the web may be hung to permit vaporization of the active ingredient to combat flies. Similarly, U.S. Pat. No. 5,229,122 utilizes a mixture of micro-encapsulated and non-micro-encapsulated active ingredients, noting that any known pesticide may be used for the purpose, including pyrethrum or a pyrethroid equivalent. The preparation is used to coat surfaces, although it is also noted that the vapor phase of the pesticides may be valuable. U.S. Pat. No. 4,765,982 is an example of the use of micro-encapsulated active ingredients to achieve a sustained release insect control effect of pyrethroids, either synthetic or “natural”. U.S. Pat. No. 6,582,714 discloses an insect control article which has a substrate that is impregnated with an active insect control ingredient that is available for passive evaporation.
However, in all of the above-described methods the release rate of the active ingredient is far from effective or optimum, which requires frequent repeated application of the essential oil products and since in many cases the active agent is also relatively costly to make or purchase, thereby increasing the cost of the essential oil products as compared to less expensive synthetic chemicals which however are often toxic and environmentally harmful.
U.S. Pat. No. 5,885,600 uses selective methods to remove certain essential oils from vegetable matter, followed by immediate protection from peroxidation, until the proper antioxidants are added. The resultant composition may then be formulated into many different items all used as insecticides, for example in veterinary use or in environmental applications.
It would be desirable to enhance the shelf life of such products and thereby extend their usability range.
Some water bodies contain undesirable zooplankton or one or more forms of harmful or undesirable insects. Thus, maintaining an acceptable water quality of water reservoirs, in particular water reservoirs that supply water for drinking and domestic consumptions, is another important application.
For example, one type of chironomids (Arthropoda: Insecta: Diptera: Chironomidae, otherwise known as bloodworms) are bottom feeder red mosquito larvae that live in water. The red larvae of this insect account for the red colour occasionally obtained in drinking water. This is only one example of the esthetic and pollution problems that Chironomids and zooplankton can cause to water bodies used as reservoirs for drinking and domestic water supplies. Furthermore, it should be noted that in order to effectively treat such chironomids and zooplankton, the formulation has to settle on the bottom of the water body or at specific depths within the water body, rather than float on the surface.
To date, there are no effective means that use non-toxic and environmentally safe agents for controlling chironomids and zooplankton. Yet further, there are no such formulations which are specifically directed at depth-residing undesirable insects or zooplankton.
For example, in U.S. Pat. No. 5,178,872 a pesticidal composition containing a microencapsulated organo-phosphorus or carbamate in a pyrethroid dispersion, is described which may also be effective against Chironomids, but does not provide any teachings on actual use against Chironomids, in particular as to the suitability of the formulation in settling on the bottom of the water body.
Another example, U.S. Pat. No. 5,741,521, discloses a biodegradable controlled release amylaceous material matrix of an agriculturally active agent such as insecticides, fungicides, fertilizers, plant growth regulants, etc. Two formulations G01S05 & G01S09 were evaluated in a bioassay trial against the eastern false wireworm. Formulation G01S905 was also evaluated in a field trial for the residual control of Chironomid larvae (bloodworms) in establishing rice crops. There is no mention of the use however of these formulations on water bodies nor is their any indication that the formulations when applied to the water will settle to the bottom to treat Chironomid and zooplankton larvae at that site.